The present invention relates to terminal assemblies for hermetic compressors, and means for preventing electrical arcing thereacross.
The terminal assembly of a hermetic compressor includes a plurality of conductor pins which extend through apertures located in a terminal body. The conductor pins are secured within these apertures by a glass insulator which electrically isolates the pins from the terminal body and the wall of the compressor housing through which the terminal body extends. The interior ends of the conductor pins are connected to lead wires running to the stator of the motor disposed within the compressor housing. The exterior ends of the conductor pins are selectively electrically connected, as through a switch device, to a source of electrical power.
During compressor operation, carbon or conductive deposits from the motor may collect on the interior surfaces of the housing and terminal assembly. These deposits may provide a conductive path between elements at differing electrical potentials, and a short circuit or arc may develop along that path. Such arcing results in resistive heating of the deposits along the conductive path, which heats the elements on which the deposits collect. Such heating is known to sometimes cause the fused glass insulators about the conductor pins to melt, thereby causing the compressor housing to leak pressurized gas at the terminal assembly.
Previous compressors including means for preventing the melting of the glass insulators have provided the insulators with an cover or coating which prevents the deposits from forming directly on the fused glass insulator. These means may include a plastic wafer or disk which is disposed over the interior of the terminal body to shield the fused glass insulator from the rest of the housing interior, the pins projecting through the wafer, their interior ends attached to the motor lead wires. Other means include coating the fused glass insulator with an epoxy, the coating extending from the conductor pins to the terminal body; the interior ends of the pins, however, remain uncoated to facilitate connection to the motor lead wires. Although these means may prevent carbon or conductive deposits from forming directly on the fused glass insulator, they do not prevent arcing between the interior ends of the conductor pins and the interior of the compressor housing. Further, resistive heating may melt the wafer or coating, the fused glass insulator melted by arcing across deposits later deposited directly on the formerly covered insulator.
It is desired to provide a means for preventing arcing across the interior of the terminal body altogether, thereby assuring the fused glass insulator will remain intact and a leak through the terminal body will not develop.